helmets

The federal government is withdrawing its long-standing claim that bicycle helmets prevent 85% of head injuries, in response to a petition filed by WABA under the federal Data Quality Act.

In 1989, a study in Seattle estimated that helmets prevent 85% of head injuries. Efforts to replicate those results during the 1990s confirmed that helmets reduce injuries, but not nearly as much as the Seattle study suggested. Yet public health advocates, government web sites, and the news media have continued to repeat the 85% factoid to the point that it has become a mantra.

Bad information can cause problems, even when it is promoted with the best intentions. If people think that helmets stop almost all head injuries, consumers will not demand better helmets, and legislators may think it makes sense to require everyone to wear one. So we asked two federal agencies to correct the misinformation, and they recently agreed to do so.

How Effective are Bicycle Helmets?

Helmets absorb the shock from a crash. If your head strikes the ground or a vehicle, your brain could be seriously shaken by the sudden deceleration. Helmets should decrease that shaking. The deceleration will be more gradual as your head depresses the foam in the helmet, rather than striking a hard surface. Helmets can also prevent head fractures by spreading the force of the impact, like the difference between being hit on the head by a rock or a beach ball with the same weight.

That’s the theory. But how often do helmets actually prevent head injuries? It’s hard to tell. Experiments on people are unethical. So researchers instead collect hospital data on people involved in bicycle crashes.

In 1989, a team of researchers from Seattle collected data about cyclists who went to area hospitals after a crash. The team was led by Robert S. Thompson, MD, who directed preventive care for the Group Health Cooperative of Puget Sound. Only 7% of the cyclists with head injuries wore helmets, but 24% of those without head injuries did wear helmets. Based on a statistical analysis they estimated that helmets had reduced the risk of a head injury by 85%. The study was published in the New England Journal of Medicine.

Doctor Thompson’s study was a “case-control study.” This type of study originally showed the link between smoking and cancer. “Case-control” is a misnomer because there is no true control group. Epidemiologists often say that case-control studies are a good way to show whether something has a good (or bad) effect on health, but not to accurately quantify that effect.

So the fundamental contribution of the Thompson study was to demonstrate that helmets do reduce the risk of head injuries. But public health advocates recognized that the 85% estimate was a good factoid for risk communication: it means that failing to wear a helmet makes you more than 6 times as likely to experience a head injury. Government web sites and newspapers repeated this factoid, to the point where it has become ubiquitous in discussions about bicycle helmets.

Meanwhile, dozens of researchers sought to replicate the Thompson findings in their own communities. They also found that helmets reduce the risk of head injuries. But they found less of a beneficial effects than Dr. Thompson found in Seattle. Some of the studies also found that helmets increase the risk of neck injuries.

In 2001, a review of all published studies found that helmets reduce the risk of head injuries by 45–71%, and increase the risk of neck injuries by 0–86%. That “meta-analysis” was updated in 2011: Helmets reduce head injuries by 25–55%, but because of the increased risk in neck injuries, the combined reduction in head and neck injuries is only 2–26%.

Yet government web sites, public health advocates, and the news media continue to repeat the 85% estimate.

Misinformation encourages helmet laws, discourages better helmets

Bicycle safety is one of WABA’s central missions, and we have strongly supported bicycle helmets for the last few decades. We require helmets on all rides that we organize. One of our sponsored projects is the Bicycle Helmet Safety Institute (BHSI), which reviews bicycle helmets and encourages improvements in their design. (BHSI raises its own funds, and is not supported by WABA membership dues.)

In the 1990s, we supported proposals to require children under the age of 16 to wear bicycle helmets, which eventually became law.

Thanks to occasional articles in the Washcycle, local cycling advocates have known for years that public health advocates overstate the effectiveness of helmets. But with all the ways by which drivers and cyclists misunderstand each other while navigating the roads, helmet effectiveness has not ranked high in our list of misconceptions to fix.

That changed this year. The Maryland Department of Transportation supported the mandatory helmet bill, based on the web site of the National Highway Traffic Safety Administration (NHTSA), which says that helmets prevent 85% of head injuries. An article in the Washington Post questioned why cyclists opposed the mandatory helmet bill, and stated that helmets prevent 80% of head injuries, according to the federal Centers for Disease Control (CDC). The mandatory helmet law was promoted by people who were relying on incorrect information on federal agency web sites.

As we prepared our testimony on the bill, we realized that most helmet research has been focused on making helmets cool, rather than more protective. Better ventilation and more fashionable designs might encourage more people to buy and wear helmets, but it does not make someone safer. Could that be because everyone is assuming that helmets are already 85% effective?

If people thought that helmets are less than 50% effective, might there be a greater focus on what really matters—a better helmet?

WABA pushed agencies to correct the misinformation

Last February, I sent emails to both CDC and NHTSA, pointing out that the 85% estimate is incorrect, and providing citations to newer research. A few weeks later, CDC thanked me for pointing out the new research. I spoke with an epidemiologist over the phone, who told me that CDC would remove the error. She confirmed the conversation in a letter.

NHTSA staff told me that they were too busy to discuss the matter. That led us to conclude that a more formal request would be necessary: The Data Quality Act requires information on federal web sites to be accurate and supported by appropriate research. So I asked NHTSA to provide the underlying documentation. NHTSA confirmed that the 85% figure was based on the Thompson study.[1]

On March 15, we sent our formal “request for correction” asking NHTSA to either remove the statement that helmets are 85% effective, or revise the quantitative estimate so that it accurately reflects the published literature. [2]

(Jim Titus is on WABA’s Board of Directors and a resident of Prince George’s County)

[1] We also asked NHTSA to support its claim that helmets are “the single most effective to prevent head injury resulting from a bicycle crash”, but it was unable to do so.

[2] Our petition also asked NHTSA to “delete all statements … asserting that wearing a helmet is the single most effective way (or device) to prevent a head injury, unless this claim has been substantiated by a peer-reviewed study showing that helmets are more effective than other ways or devices for preventing head injuries.”

[3] NHTSA did not, however, agree to our request that the agency either substantiate or remove the claim that “wearing a helmet is the single most effective way (or device) to prevent a head injury.” NHTSA said that WABA had not met its burden of proof. Evidently, WABA and NHTSA disagree on whether NHTSA is required to provide at least one study showing its statement to be correct, before WABA would be required to show the statement to be wrong. We are thinking about whether to appeal.

On Tuesday morning, the Environmental Matters Committee of the Maryland House of Delegates will hold a hearing on House Bill 339 to require that every person operating a bicycle in Maryland wear a helmet. This bill is bad policy.

Mandatory helmet laws cause fewer people to bicycle, and when fewer people bicycle, cycling becomes less safe. So much less safe, in fact, that decreased ridership increases the individual cyclist’s risk of injury more than wearing a helmet decreases risk of injury.

This does not mean that bicyclists should not wear helmets. We encourage bicyclists to wear helmets. However, there are several reasons why people who are deeply committed to bicyclist safety oppose mandatory helmet laws.

Mandatory helmet laws decrease ridershipNumerous studies of places that have enacted helmet laws have shown this to be true. The most commonly-cited study—Dorothy Robinson’s “No Clear Evidence from Countries that have Enforced the Wearing of Helmets”—examined data from New Zealand, from Nova Scotia, Canada, and from several states in Australia. In each place, the mandatory helmet law significantly decreased ridership, from 20% to 44% with an average of 37.5%.

(One can debate whether Maryland can expect a decrease of this magnitude. There is no local data available, so this analysis uses the average of 37.5%. But even if the decrease is only 20%, the lowest Robinson observed, even half of that, the result is the same.)

Lower ridership makes bicycling less safe.We are defining “safety” as the likelihood of a bike-auto crash. By saying that decreased ridership makes bicycling less safe, we mean that a decreased rate of bicycling within a population is correlated with increased crash rates, and vice versa.

Across the independent sets of data from these many jurisdictions, Jacobsen finds a consistent, inverse, curvilinear relationship between bicycling and injury rates, determining that “the total number of pedestrians or bicyclists struck by motorists varies with the 0.4 power of the amount of walking or bicycling respectively.” Expressed simply, more people biking leads to fewer per capita crashes while fewer people biking leads to more per capita crashes.

Jacobsen also derives a formula for how this affects the individual cyclist: “Taking into account the amount of walking and bicycling, the probability that a motorist will strike an individual person walking or bicycling declines with roughly -0.6 power of the number of persons walking or bicycling.” In other words, as more people bicycle, the per capita risk to each bicyclist of a crash decreases; if fewer people bicycle, the per capita risk to each bicyclist increases.

Helmets do not make cyclists as safer as commonly thoughtFor the individual, of course, the story is different. Wearing a helmet is likely safer than not wearing one. This is true for bicyclists; it is also true for people who are skydiving, rock climbing, sitting under an oak tree, or taking a bath. Individually, we make our decisions based on our own risk tolerances and values, and many of us choose to wear helmets and encourage our loved ones to do so.

But at the broader level, where we ought to analyze legislation and public policy, how much safer will a helmet make a person in a bike crash that leads to a head impact? This is a topic of debate and uncertainty, but as research methods improve we move further from some of the magical thinking that took hold due to early estimates—derived from emergency room data rather than population data—that suggested helmet effectiveness rates of 85% and above.

Generally, those estimates came from retrospective studies that looked at people with head injuries in emergency rooms and compared the numbers who lived and died, and whether they were wearing helmets when they were hit. When more recent studies have attempted to compile these data into meta-analyses with more informative sample sizes, their results do not approach the long-accepted 85% level. Some show a smaller effect; others, none at all. In fact, in population-level studies focusing on hospitalization rather than emergency room visits, helmets have no discernible, statistically significant effect on hospitalization rates. (Jacobsen 2012)

Recent studies that have focused on overall health, rather than simply crash mortality rates, have shown that the individual and public health benefits grossly outweigh the costs, by a factor of 20:1. (De Jong 2012)

The mandatory helmet law in Maryland will increase danger for Maryland cyclistsAssuming that the helmet law will decrease cycling by the 37.5% average in Maryland, the total Maryland cycling population, post helmet law, would shrink to only 62.5% of the current cycling population. Assuming also that Jacobsen’s safety-in-numbers effect holds true in Maryland—as it has consistently throughout California and across Europe—the number of motorists colliding with people bicycling will increase by roughly 17.1% per capita (1-0.6250.4=0.171)

For the individual, these assumptions mean that the likelihood of injury from a crash with a motor vehicle would increase by roughly 33% (0.625-0.6=1.326)—regardless of whether the individual wears a helmet. The increased risk comes solely because mandatory helmet laws take people off bicycles, and fewer people on bicycles makes the remaining bicyclists less safe. Substantially.

Maryland does not keep much data on bicycling, but one piece of data that we do have is that in 2010, there were 734 reported bicycle crashes in Maryland. Looking only at this data—and assuming ridership decreases by 37.5% from the helmet law in Maryland—we might expect only 459 crashes instead of 734.

However, this expectation is wrong. Due to the decreasing “safety in numbers,” we would instead expect to see 537 crashes, or 78 additional crashes directly attributable to the mandatory helmet law. So even though the total number of crashes might decrease, that is not because the law has made cyclists safer; it is because substantially fewer people are riding bikes, and those that still ride are measurably less safe, because of the law.

Discouraging cycling runs counter to Maryland’s other prioritiesThe state of Maryland has launched, or is poised to launch, two programs dedicated to encouraging cycling. The mandatory helmet law would undermine the success and safety of both.

First, knowing the overall benefits of biking to public health and well-being, transportation, economic development, and other public priorities, the state of Maryland initiated a campaign to get more people riding bikes. Maryland’s Department of Transportation introduces the campaign on their website with:

Governor O’Malley’s Cycle Maryland initiative is an effort to encourage more Marylanders to get out and ride, and to make bicycling a true transportation alternative. Cycling is a great way to connect to your community, support a cleaner environment, encourage a healthier lifestyle, reduce household transportation costs and enjoy Maryland’s magnificent landscape.

With the mandatory helmet law reducing ridership, Maryland will be left with more people to figure out how to move, and will have to treat more people for health problems associated with sedentary lifestyles.

Second, Maryland has contributed funds to expand the popular and successful Capital Bikeshare program to Montgomery County. Due to the nature of bikesharing, users are less likely to wear helmets, more likely to be casual rather than experienced users, and more likely to be operating in urban environments with motor vehicles. So perhaps the legislators proposing this mandatory helmet bill mean to ensure the safety of those riders, before bikesharing arrives in the state?

However, again, consider the data: Capital Bikeshare users have logged over 3.4 million trips, with an approximately 38% lower helmet usage rate than the general population. (Kraemer 2012) There have been zero fatalities and only one head injury. That is roughly one crash for every 88,000 miles ridden! Yet by driving potential cyclists away, a mandatory helmet policy would undermine the likelihood of success of the program in Montgomery County, Baltimore, and other areas statewide.

That safety record speaks for itself and shows that biking is not an inherently dangerous activity. Mandatory bicycle helmet laws falsely portray it as such, and in doing so create a false sense of danger that limits ridership and undermines the many positive impacts of mass cycling for Maryland.

“Contributory negligence” makes the law especially harmfulAnd finally, some believe that this law is acceptable and benevolent and will not have these impacts because there is no fine for violation. But this law has other, even more dire consequences for violators.

Maryland, like the District and Virginia, is a “contributory negligence” jurisdiction. That means if the victim of a crash contributed in any way to her own injury, she can claim no civil recovery for her damages. In Maryland, violation of a law is negligence per se.

Thus, it is possible that a cyclist who rides the bus to work on a rainy morning but chooses to take a bikeshare bike home when the weather clears, and suffers permanent brain injury when a drunk driver veers into a bike lane and strikes her, could be denied any civil recovery as a result of not wearing a helmet.

Is this the transportation future we want in Maryland? Is this the sort of public policy we hope to encourage?

ConclusionIn Maryland, we can anticipate a mandatory helmet law to reduce bicycle ridership by 37.5% (along with its accompanying public health, environmental, and economic benefits), per capita crashes to increase by 17%, and the per capita risk of a crash to increase by 33% for every person riding a bike in the state of Maryland, regardless of whether he or she wears a helmet.

In a broader sense, these laws are a form of victim blaming—telling bicyclists that it is our responsibility to avoid the risk of injury by padding ourselves, rather than the state’s to design a transportation network capable of moving non-motorists with a decent level of safety and efficiency.

WABA opposes a mandatory helmet law in Maryland because it is bad policy based on accepted, tested, and peer-reviewed data—not just some libertarian philosophy or desire of cyclists to “feel the wind in our hair.”

Fundamentally, we do believe that the legislators proposing this mandatory helmet law hope to do what is best for bicyclist safety, but they have significantly erred in determining what will, in fact, be best. They have the power to impose new risks on each of us who rides a bike, even when we wear helmets. We hope they will consider this information seriously and decide that a mandatory helmet law is a bad policy for the state of Maryland.

If you’d like to voice your opposition to Maryland’s House Bill 399, you can do so here.

Kraemer, John D., Jason S. Roffenbender, and Laura Anderko. 2012. Helmet Wearing Among Users of a Public Bicycle-Sharing Program in the District of Columbia and Comparable Riders on Personal Bicycles. American Journal of Public Health 102 (8): e23-e25.

Robinson, Dorothy L. 1996. No Clear Evidence from Countries that Have Enforced the Wearing of Helmets. British Medical Journal 332 (7543): 722-725.

Last night, we asked you to take action to oppose a mandatory helmet law introduced in the Maryland House of Delegates’ Committee on Environmental Matters. In response, some of you asked for additional information on the “debatable” effects on bicyclists’ safety and the negative impacts on cycling that a mandatory helmet law would have.

We vocally and overwhelmingly approve of helmets here at WABA. All of our staff and volunteers wear them, we require participants to wear them at all WABA events, and we teach how to wear them properly in all WABA education classes. Helmets provide an important last line of defense in the safety equation during a crash. When everything else has gone wrong, helmets have saved many bicyclists from more serious injuries or even death. We don’t get on our bikes without our helmets and we strongly encourage every cyclist out there to wear one.

However, mandatory helmet laws requiring all bicyclists to wear helmets are not effective at increasing helmet usage without significantly affecting ridership. There are many studies that show helmet usage increases when laws are passed—but critically, not without a negative effect on overall bicycle ridership. In Australia, ridership dropped 37.5 percent between 1985 and 2011 after such a law was passed. During the same time, population growth was three times higher than the growth of cycling, meaning following the passage of a mandatory helmet law, there was a net decrease in bicycling.

These laws negatively impact bicycle ridership by throwing up one more barrier (financially and behaviorally) to bike riding. Therefore, a potential bicyclist will be driven to choose another mode of transportation. Additionally, a recent New York Times article quoted Piet de Jong, a professor in the department of applied finance and actuarial studies at Macquarie University in Sydney: “Pushing helmets really kills cycling and bike-sharing in particular because it promotes a sense of danger that just isn’t justified—in fact, cycling has many health benefits.” Jong has studied the public health impacts of bicycling and has concluded that the positive health benefits outweigh risks of helmetless riding 20 to 1. In a country in the midst of an obesity epidemic, encouraging a few miles of bicycling everyday could lead to a considerable reduction in overall healthcare costs. And as jurisdictions like Montgomery County consider bikesharing programs, it’s important that those programs are accessible. Mandatory helmet laws in Maryland could potentially kill the momentum for bikesharing, as the law would promote a sense of danger for cycling, ignoring the obvious overall health benefits.

And finally, these laws are merely an easy “fix” for legislators that distract from larger safety issues—such as the lack of safe, separate and comfortable places to ride. Adults and kids need safe spaces to ride on our roads that are separate from cars. We at WABA believe there are better legislative ways to keep bicyclists safe, such as better and more targeted enforcement of current traffic laws (especially distracted driving), increased bicyclist education, and, most importantly, the construction of separated bicycling facilities.

Helmets are an important part of keeping bicyclists safe and WABA enthusiastically supports their promotion and use, but mandatory helmet laws do more harm than good.

At WABA, we encourage and teach safe and responsible cycling practices, including helmet use. But we do not believe that mandatory helmet laws are the proper approach. While their impact on safety is debatable, their impact on cycling rates (especially in jurisdictions implementing or seriously studying bikesharing) is clearly negative.

Please CLICK HERE to let the Environmental Matters Committee know that you are a responsible cyclist and a responsible adult capable of making your own decision regarding safety equipment, and that you OPPOSE HB 339 and its imposition of a mandatory helmet requirement.

Summary: Is the Swedish airbag bike helmet a reality? Can it really protect the way a traditional helmet does? We are waiting to see test results and answer a lot of questions.

These British newspaper / blog articles with an embedded video introduces Swedish headgear that is based on the airbag principle, with an inflating protective bonnet designed to deploy when the rider is about to crash.
Airbag helmets have been the subject of conversation for years, often accompanied by photos of riders with balloons on their heads. But this one appears to be a serious attempt to put the mechanism to work. The device is a project of two Swedish design students, and other sources say it is expected to be on the UK market in 2011 at a price of 260 British pounds.

The airbag is nylon, and inflates with a gas generator when embedded gyros and accelerometers tell it a crash is taking place. The gyros have to be powered during use, so the Chieftan has a rechargeable battery. That seems like a real drawback to us, since the user has to be aware of the battery charge level (there are led indicators) and remember to keep it charged. After a crash the manufacturer wants the headgear back to check its “black box” for recorded movements prior to your crash. They offer a discount on the replacement. That implies that this is not a multi-use product.

If the device can detect all crash scenarios, the mechanism could be used to deploy other forms of protection for other body parts.

The video shows a test dummy on a bicycle struck from behind by a car indicated as moving at 20 kph (12 mph). The dummy is thrown over the hood and impacts its head on the flat part of the windshield. The bag deploys prior to the impact.

That is one specific scenario. But did the helmet perform? You can see the helmet bottom out and let the head hit the windshield anyway, and there is no instrumentation registering how many g’s the dummy head saw. And what would happen in a simple fall? Collision with a tree branch or utility pole? The mirror of a bus, or the front of a truck? Another impact after the bag begins to lose air?

Helmet lab testing normally includes testing wet, cold and hot samples. They are tested against rounded anvils and curbstone anvils as well as flat ones. How well would this device perform against a grapefruit-shaped anvil, or one that was the shape of a curb?

It is not possible to answer questions based on one article and video. There is no need to be too skeptical until we see more. That same thought applies to the helmet with a fiberboard helmet liner introduced by design students in the UK last month.

Perhaps the most important immediate news is that at least somebody is trying to solve the shared bike program helmet problem. Shared bike programs all over the world are in need of an easily transportable helmet or one that can be dispensed from vending machines at very low cost for users of shared bicycle programs who did not think to bring a helmet. There is at least one folding helmet from Dahon currently available in Europe, but it does not meet US standards and is expensive. We have been talking to manufacturers about shared bike helmets recently, but getting glazed looks that tell us they are thinking “there is not enough market to make it pay.”